EAD
AP
you will be applying for EAD under category (c)(9)
further you do not have to pay any fees for filing I-765. see instructions for I-765 page 8 section titled Renewal EAD

when to renew EAD?
To extend an employment authorization card, an application for renewal must be filed around 90 days prior to the expiration date printed on the card. An application for renewal of a work permit must be filed and accepted by the USCIS prior to the expiration of the card that was initially granted to the applicant. Applicants must remember that they cannot file applications for renewal more than 120 days before their original permits expire.
also you don’t need to pay any fee for AP:

on page 2 of AP, you need to select:

more on EAD/AP:
Q4. If I receive this card, does that guarantee my re-entry into the United States if I travel?
A4. No. This card authorizes parole, not admission, to the U.S. Parole is not an admission or “entry”. If you obtain this card, you may use it to travel abroad and return to the U.S. Upon arriving at a port-of-entry, you should present the card to a Customs and Border Protection (CBP) Officer to request parole. Issuance of an Advance Parole document does not guarantee that CBP will parole you into the U.S. If parole is granted, you will be permitted to come into the U.S. as a parolee, but will not have been ‘admitted”. Individuals who have been unlawfully present in the U.S. and subsequently depart and seek re-entry through a grant of parole may be inadmissible and ineligible to adjust their status.
Below are the list of documents and Complete Detials :
For EAD renewal:
1. Fill out and sign form I 765
2. Two pp photos with A-Number written on the back of them (Recent photos)
3. I 765 Approval Notice and Receipts
4. Photocopy of 485 receipt (i-797)
5. Form G1145 for E Notification for application acceptance ((Optional for e-mail, SMS notification))
6. Photocopy of Current EAD/AP combo card
7. Bar codes page attached to the previous EAD/AP approval
8. Copy of Marriage Certificate for dependent only
Other Details:
1. NO FEE ( check i-765instr.pdf for confirmation ) If u file ur 485 after July 30,2011
2. Address to send: depends on where you live, see page 10 of the I765 instructions document.
3. http://www.uscis.gov/files/form/i-765instr.pdf
For AP:
1. Fill out and sign form i-131
2. Two pp photos with A-Number written on the back of them
3. Photocopy of 485 receipt/ Approval Notice (i-797)
4. I-485 Receipts
5. Form G1145 for E Notification for application acceptance ((Optional for e-mail, SMS notification))
6. Photocopy of Current EAD/AP combo card
7. Bar codes page attached to the previous EAD/AP approval.
8. Copy of Marriage Certificate for dependent only
Other Details:
1. No FEE ( check i-131instr.pdf for confirmation ) If u file ur 485 after July 30,2011
2. Address to send: depends on where you live, see page 10 of the I765 instructions document.
3. http://www.uscis.gov/files/form/i-131instr.pdf
Note: Just as a practice, I put each application in a manilla envelope and write the name, A# and form number on the outside for each applicant. Then I put all of the envelopes in a courier package (FedEx, UPS, Express Mail) and send it to the USCIS. I’ve never had a problem with that approach and none of the applications have ever been lost or separated.
Note:If u are applying Combo Card, Pls send Both the documents (I-131 (AP) & I-765 (EAD)) to I-765-EAD address..
Here is Cover letter Sample for both EAD and AP:
To,
USCIS
ADDRESS
Dear Sir/Madam:
Sub: I-765, Extension Application for my Employment Authorization Document, , Alien # – Supporting documents
Please find the following documents in support of the I-765 Extension Petition for Employment Authorization Document.
• Completed form I-765, Application for Employment Authorization
2 color photographs (A# and Name lightly printed in the back);
Copy of previously approved Employment Authorization Card(Front)
Copy of previously approved Employment Authorization Card(Back)
• Copy of I-797C, Notice of Action, receipt of filing I-485
Copy of Previously approved EAD mailer
I appreciate very much if you could do the needful, process the petition and extend my EAD at your earliest convenience.
Sincerely,